In this paper I discuss the role played by the 'categorical imperative' in the thought of Jean-Luc Nancy. I argue that, while this is a theme of major importance in Nancy's work, its overall significance is not immediately evident: on the surface, Nancy appears to be affirming the abstract exigency of the imperative while at the same time depriving it of any possible concrete force. I maintain, however, that a close reading of this theme in terms of other crucial themes in Nancy's writing (namely: 'interruption' and the Heideggerian notion of 'Being-with' [Mitsein, être-avec]) reveals that Nancy's imperative does have concrete implications; indeed, it demands that we rethink the relation between responsibility and the concrete as such. Key Words: communication • community • Jacques Derrida • Martin Heidegger • imperative • Jean-Luc Nancy • responsibility.